President Obama toured the U.S. Holocaust Museum in Washington today joined by Holocaust survivor, author and Nobel Laureate, Elie Wiesel. Mr. Obama said the U.S. must never again allow such atrocities to take place.

As NPR's Don Gonyea reports, the president also announced new tools to punish countries that use technology to track and target their citizens.

DON GONYEA, BYLINE: President Obama and Elie Wiesel walked slowly through the museum's Hall of Remembrance, looking at exhibits, pausing at the eternal flame, talking quietly outside the range of microphones. Afterward, each spoke to a packed auditorium, Wiesel asking the most basic question, why did the Holocaust happen?

ELIE WIESEL: One thing we do know, that it could have been prevented. The greatest tragedy in history could have been prevented.

GONYEA: If, he said, civilized nations had acted. The president then spoke of another tour these two men took almost three years ago at the Buchenwald concentration camp where Wiesel had been imprisoned.

PRESIDENT BARACK OBAMA: And I recall how he showed me the barbed-wire fences and the guard towers, and we walked the rows where the barracks once stood, where so many left this earth, including Elie's father, Shlomo.

GONYEA: The president also turned his focus to the present, acknowledging that the U.S. cannot control every event.

OBAMA: And when innocents suffer, it tears at our conscience. Elie alluded to what we feel as we see the Syrian people subjected to unspeakable violence simply for demanding their universal rights. We have to do everything we can.

GONYEA: Mr. Obama announced new sanctions against nations that commit grave human rights abuses through technology that includes cell phone tracking and monitoring citizens on the Internet. In part, it is also a recognition that military intervention is not a tool that can be used quickly and without risk. In attendance today was former Bush administration Homeland Security Secretary Michael Chertoff. He praised the steps the president unveiled.

MICHAEL CHERTOFF: It's meaningful to cut off access to technologies that would be used to repress and persecute at particularly the stages of a developing tragedy, being able to slow up or stop a genocide or crimes against humanity from actually coming to fruition is a very, very important step.

GONYEA: But, he said, the challenge for every president facing such a crisis is what to do and when to do it. Michael Abramowitz directs the genocide prevention program at the Holocaust Memorial Museum.

MICHAEL ABRAMOWITZ: It is totally appropriate for us to ask any of our leaders, not just the president of the United States, but other leaders, are you doing enough. We can always do better. And that's why I was so particularly moved by seeing Elie Wiesel on the stage today talking to President Obama and talking about real life situations today, about Syria, about Iran. You know, that was a reminder, that was a level of accountability that is really important.

GONYEA: And which awaited the president as he made the short trip back to the White House from the museum.